Passive long range acoustic sensor

Abstract

This Passive Long Range Acoustical Sensor relates to means of sensing acoustical sources and signals, including multi-channel acoustical signals, such as various types of sounds, vibrations, flutter, turbulence, and the like, and at long distances through a natural optical channel, without the use of a laser or other artificial illuminating means. A modified multi-channel embodiment of the Passive Long Range Acoustical Sensor may use a combination of natural optical channels and active illumination means, such as laser or other artificial illuminating means, of producing additional optical channels.

1. A Passive Long Range Acoustical Sensor, comprised essentially of:
 a. a telescope with a photosensitive element positioned at said telescope's focal plane; 
 b. said photosensitive element is in communication with an amplifier; 
 c. said amplifier is in communication with a DC coupled automatic gain control that stabilizes a DC gain from an optical communication channel; 
 d. and the amplifier is in communication with a band pass filter that passes a desired audio signal; and 
 e. said band pass filter is in communication with a listening means. 
 
   
   
     2. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 1 , and further comprised of a recording means that is also in communication with the band pass filter. 
   
   
     3. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 1 , and further comprised essentially of:
 a. additional photosensitive elements, each said additional photosensitive elements capable of sensing a set of different glints in a scene, and being in communication with an additional amplifier; 
 b. each said additional amplifier being in communication with an additional DC coupled automatic gain control; 
 c. each said additional DC coupled automatic gain control being in communication with an additional band pass filter; 
 d. and each said additional band pass filter is in communication with said listening means. 
 
   
   
     4. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 1 , and further comprised essentially of an additional photosensitive element, with the photosensitive element and said additional photosensitive element each sensing a spatially separated glint, and said photosensitive element and the additional photosensitive element each being in multiplexed communication with said amplifier, said DC coupled automatic gain control and the band pass filter, and such that said band pass filter is in communication with a stereophonic listening means. 
   
   
     5. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 3 , wherein a plurality of band pass filter outputs are connected to a correlator that computes differential acoustic path delays from intensity variation of said set of different glints in a scene for at least one acoustic source. 
   
   
     6. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 1 , wherein said automatic gain control uses a feedback gain stabilizing architecture. 
   
   
     7. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 1 , wherein said automatic gain control uses a feedforward gain stabilizing architecture. 
   
   
     8. A Passive Long Range Acoustic Sensor; comprised essentially of that recited in  claim 3 , and further comprised of a correlator that computes differential acoustic path delays from intensity variations of said set of different glints, and for at least one acoustic source. 
   
   
     9. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 8 , wherein said correlator is in communication with a programmable time delay system, and said programmable time delay system can time align a set of acoustic paths from said acoustic source to said the set of different glints to cause coherent enhancement of a desired acoustic source. 
   
   
     10. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 8 , wherein said correlator is in communication with a programmable time delay system, and said programmable time delay system can time align a set of acoustic paths from said acoustic source to said the set of different glints to cause coherent cancellation of an interfering acoustic source. 
   
   
     11. A Passive Long Range Acoustic Sensor, comprised essentially of:
 a. a telescope with a plurality of photosensitive elements positioned at said telescope's focal plane; 
 b. said plurality of photosensitive elements are capable of sensing multiple spatially separated glints, and each of the plurality of photosensitive elements are in multiplexed communication with an amplifier; 
 c. said amplifier is in communication with a multiplexed band pass filter; 
 d. said band pass filter is in communication with a correlator that computes differential acoustic path lengths from intensity variations of a set of spatially separated glints and for at least one acoustic source. 
 
   
   
     12. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 11 , with said correlator in communication with a Programmable time delay system, wherein said programmable time delay system can time align a set of acoustic oaths from said acoustic source to said set of spatially separated glints to cause coherent enhancement of the acoustic source, followed by a multichannel recording means. 
   
   
     13. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 11 , and further comprised essentially of:
 a. additional photosensitive elements, with each said additional photosensitive element being in communication with an additional amplifier; 
 b. and each said additional amplifier being in communication with an additional filter; 
 c. and each said additional filter being in communication with the correlator. 
 
   
   
     14. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 13 , wherein the amplifier and each additional amplifier is followed by an optical carrier referenced gain stabilizing feedback architecture. 
   
   
     15. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 11 , wherein the amplifier is followed by an optical carrier referenced gain stabilizing feedback architecture. 
   
   
     16. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 13 , wherein the amplifier and each additional amplifier is followed by an optical carrier referenced gain stabilizing feedforward architecture. 
   
   
     17. A Passive Long Range Acoustic Sensor, comprised essentially of that recited in  claim 11 , wherein the amplifier is followed by an optical carrier referenced gain stabilizing feedforward architecture. 
   
   
     18. A Passive Long Range Acoustic Sensor System, comprised essentially of a plurality of the Passive Long Range Sensors as recited in  claim 1 , and such that each of said plurality of the Passive Long Range Sensors are sensing a spatially separated glint, and each of the plurality of Passive Long Range Acoustic Sensors being in communication with a common signal processing computer that includes a correlator that computes differential acoustic path delays from the intensities of said spatially separated glints for at least one acoustic source. 
   
   
     19. A method for passively sensing remote acoustical sounds, comprised essentially of the steps of:
 a. aligning a telescope so that a remote glint is viewed and sensed by a photosensitive element located at said telescope's focal plane; 
 b. amplifying a signal generated by said photosensitive element; 
 c. reducing low frequency amplitude noise modification by stabilizing a glint channel gain with a DC coupled automatic gain control; 
 d. filtering said signal with an audio band pass filter, and 
 e. transmitting the signal to a listening means. 
 
   
   
     20. A method for passively sensing remote acoustical sounds, comprised essentially of the steps recited in  claim 19 , and further comprised of additional photosensitive elements located at the focal plane of the telescope, to allow viewing and sensing of multiple remote glints, amplifying each said photosensitive element's signal, stabilizing said glint channel gain with a DC coupled automatic gain control, and filtering each of the photosensitive element's amplified signal with a band pass filter, and transmitting each said photosensitive element's amplified and filtered signal to a listening means.